Investigation of the Impact of Inverter-Based Generators on Protection Schemes

At low penetration levels, Inverter Based Generators (IBG) have minimal impact on grid stability and on the network short circuit current during fault conditions; hence, they do not significantly affect the grid protection system. However, this changes as the penetration level of IBG increases. Increased penetration of IBG in the power grid has prompted regulators to incorporate Low Voltage Ride Through (L VRT) capability in IBG grid connection standards to ensure grid stability. This L VRT capability results in a more substantial short-circuit current that IBGs will contribute during fault conditions. Unfortunately, the short-circuit current contribution of IBG differs from traditional Synchronous Generators (SG). The uniqueness of the short-circuit contribution renders traditional protection schemes, designed for conventional synchronous generators, unreliable. Hence, there is the need for protection relay and inverter engineers to better understand the challenges posed by this IBGs and proffer solutions to ensure reliable operation of protection schemes. This paper presents the fault characteristics of different IBGs to understand their behavior during fault conditions and investigates common protection scheme mis-operation and trending solutions.